Back pressure; was Re: got my 2.5" centre pipe!

[scourge@cogeco.ca (Scourge)]

I'm going to admit right now that I have no idea what I'm talking about,
lol.
And this is kinda long.....

But in my experience..........I had an 86' golf, MZ engine rated at 90 hp
and 98 ft. lbs. everyone who drove it (that was into VW's) agreed that it
had more balls then it should. All that had been done was a butchering of
the exhaust. It was a non-cat car, had a single resonator and a single
desiel muffler. The tailpipe was MUCH smaller then factory for that car. And
when it was running at idle it sounded "restricted". At high rpm it sounded
like a dirt bike. The only explanation I got for it's extra power was that
the higher backpressure would increase the torque...sounds good to me, lol

Then, when I got my rocco it had no muffler. Also a non-cat car, one
resonator and the factory pipe ran to the axle. It was LOUD, and had wayyy
more power then my golf but lacked the torque(this is a 1.7). I now have 4-2
manifold with  dual downpipe(same as before), stainless gutted cat, 2"
stainless back to a single 2" in 2 1/4" out muffler.....sounds kool, nice
and deep but not too loud. After it went on, the car didn't rev out quite as
quick and lost a fair bit of it's top end power. But what it lost was made
up for in torque.
Hope this helps someone....if not, then I just wasted ur time!!!
thanx for reading, lol


"The George"

----- Original Message -----
From: "Scott F. Williams" <sfwilliams@comcast.net>
To: "Andrew Basterfield" <list@cemetery.homeunix.org>; "Dan Bubb"
<jdbubb@ix.netcom.com>
Cc: <drew@scirocco.cs.uoguelph.ca>; <skerocdriver@juno.com>;
<scirocco-l@scirocco.org>
Sent: Thursday, March 13, 2003 2:18 PM
Subject: RE: Back pressure; was Re: got my 2.5" centre pipe!


> Andrew Basterfield wrote:
> > Gas motors need back pressure because the factory fuelling
> > and ignition maps are set up with the standard air intake and
> > exhaust system.
>
> Let's amend that statement to say: "Factory fueling and ignition maps are
> set up [to work with] the standard air intake and exhaust systems." -in
> other words with some backpressure. It is a fact, however, that gas motors
> do *NOT* need back pressure ultimately speaking.
>
> It is certainly plausible that reducing backpressure may result in a power
> loss if the resulting operating conditions are not compatible with the
> engine management's factory tuning.In general, however, maximum power will
> be extracted from any properly-tuned internal combustion engine when there
> is zero or even negative pressure in the exhaust system.
>
> We battled about this very subject sometime last year. In fact, the
infamous
> fuel injector controversy reminded me of the "back pressure wars" that
came
> several months before. In contrast to that thread's outcome, the powers of
> good triumphed over the grim forces of evil. (chuckle)
> --
> Scott F. Williams
> NJ Scirocco nut
> '99 Subaru Impreza 2.5 RS
> Mazda 323 GTX turbo "assaulted" vehicle
> Golf GTI 16v "rollycar"
> ClubVAC: "Roads found. Drivers wanted."
>
>
>
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